This disclosure relates to alkylation catalysts and in particular to alkylation catalysts comprising magnesium oxide or iron oxide, as well as combinations thereof and their methods of preparation and use.
Processes for the ortho-alkylation of hydroxy aromatic compounds, in some cases, involve vapor phase reaction of a hydroxy aromatic compound, e.g., phenol, with an alkyl alcohol using an alkylation catalyst. Ortho-alkylated hydroxy aromatic compounds are well known for application as disinfectant, wood preservatives and as a monomer in the synthesis of some high-performance thermoplastic products.
In such ortho-alkylation processes, it is desirable for the catalyst to have high activity i.e. it must have as long and active a life as possible. Moreover, the catalyst should have very good ortho-selectivity. Many of the ortho-alkylation catalysts used are known to produce a mixture that often contains a high proportion of para-alkylated products and consequently such catalysts have marginal commercial utility. For example, ortho alkylation of phenol to produce 2,6-dimethyl phenol (2,6-xylenol), results in the formation of unwanted by-products such as ortho-cresol, anisole, and trialkylated products such as 2,4,6-trimethyl phenol (mesitol), resulting in lower selectivity. Over alkylation to mesitol results in higher phenol and methanol usage thereby increasing the overall cost of production of 2,6-xylenol. Moreover, additional purification steps and expense are needed to remove the mesitol and provide a proper disposal method.
It is known that selectivity and activity are related to the characteristics of the ortho-alkylation catalyst, and to the manner in which it is prepared. Various methods of preparing magnesium oxide based catalysts with desired catalyst activity and selectivity for ortho-alkylation of hydroxy aromatic compounds have been attempted which involve the use of promoters and the like.
However, there exists an ongoing need for improvement in catalyst activity and catalyst selectivity for ortho-alkylation of hydroxy aromatic compounds so as to favor production of the desired alkylated compound substantially free of unwanted by-products thereby rendering such ortho-alkylation process more productive and cost-effective.